import os
import os.path as op
import gc
import json
from typing import List
import logging


def generate_lineidx(filein: str, idxout: str) -> None:
    idxout_tmp = idxout + '.tmp'
    with open(filein, 'r') as tsvin, open(idxout_tmp, 'w') as tsvout:
        fsize = os.fstat(tsvin.fileno()).st_size
        fpos = 0
        while fpos != fsize:
            tsvout.write(str(fpos) + "\n")
            tsvin.readline()
            fpos = tsvin.tell()
    os.rename(idxout_tmp, idxout)


def read_to_character(fp, c):
    result = []
    while True:
        s = fp.read(32)
        assert s != ''
        if c in s:
            result.append(s[: s.index(c)])
            break
        else:
            result.append(s)
    return ''.join(result)


class TSVFile(object):
    def __init__(self,
                 tsv_file: str,
                 if_generate_lineidx: bool = False,
                 lineidx: str = None,
                 class_selector: List[str] = None):
        self.tsv_file = tsv_file
        self.lineidx = op.splitext(tsv_file)[0] + '.lineidx' \
            if not lineidx else lineidx
        self.linelist = op.splitext(tsv_file)[0] + '.linelist'
        self.chunks = op.splitext(tsv_file)[0] + '.chunks'
        self._fp = None
        self._lineidx = None
        self._sample_indices = None
        self._class_boundaries = None
        self._class_selector = class_selector
        self._len = None
        # the process always keeps the process which opens the file.
        # If the pid is not equal to the currrent pid, we will re-open the file.
        self.pid = None
        # generate lineidx if not exist
        if not op.isfile(self.lineidx) and if_generate_lineidx:
            generate_lineidx(self.tsv_file, self.lineidx)

    def __del__(self):
        self.gcidx()
        if self._fp:
            self._fp.close()

    def __str__(self):
        return "TSVFile(tsv_file='{}')".format(self.tsv_file)

    def __repr__(self):
        return str(self)

    def gcidx(self):
        logging.debug('Run gc collect')
        self._lineidx = None
        self._sample_indices = None
        #self._class_boundaries = None
        return gc.collect()

    def get_class_boundaries(self):
        return self._class_boundaries

    def num_rows(self, gcf=False):
        if (self._len is None):
            self._ensure_lineidx_loaded()
            retval = len(self._sample_indices)

            if (gcf):
                self.gcidx()

            self._len = retval

        return self._len

    def seek(self, idx: int):
        self._ensure_tsv_opened()
        self._ensure_lineidx_loaded()
        try:
            pos = self._lineidx[self._sample_indices[idx]]
        except:
            logging.info('=> {}-{}'.format(self.tsv_file, idx))
            raise
        self._fp.seek(pos)
        return [s.strip() for s in self._fp.readline().split('\t')]

    def seek_first_column(self, idx: int):
        self._ensure_tsv_opened()
        self._ensure_lineidx_loaded()
        pos = self._lineidx[idx]
        self._fp.seek(pos)
        return read_to_character(self._fp, '\t')

    def get_key(self, idx: int):
        return self.seek_first_column(idx)

    def __getitem__(self, index: int):
        return self.seek(index)

    def __len__(self):
        return self.num_rows()

    def _ensure_lineidx_loaded(self):
        if self._lineidx is None:
            logging.debug('=> loading lineidx: {}'.format(self.lineidx))
            with open(self.lineidx, 'r') as fp:
                lines = fp.readlines()
                lines = [line.strip() for line in lines]
                self._lineidx = [int(line) for line in lines]

            # read the line list if exists
            linelist = None
            if op.isfile(self.linelist):
                with open(self.linelist, 'r') as fp:
                    linelist = sorted(
                        [
                            int(line.strip())
                            for line in fp.readlines()
                        ]
                    )

            if op.isfile(self.chunks):
                self._sample_indices = []
                self._class_boundaries = []
                class_boundaries = json.load(open(self.chunks, 'r'))
                for class_name, boundary in class_boundaries.items():
                    start = len(self._sample_indices)
                    if class_name in self._class_selector:
                        for idx in range(boundary[0], boundary[1] + 1):
                            # NOTE: potentially slow when linelist is long, try to speed it up
                            if linelist and idx not in linelist:
                                continue
                            self._sample_indices.append(idx)
                    end = len(self._sample_indices)
                    self._class_boundaries.append((start, end))
            else:
                if linelist:
                    self._sample_indices = linelist
                else:
                    self._sample_indices = list(range(len(self._lineidx)))

    def _ensure_tsv_opened(self):
        if self._fp is None:
            self._fp = open(self.tsv_file, 'r')
            self.pid = os.getpid()

        if self.pid != os.getpid():
            logging.debug('=> re-open {} because the process id changed'.format(self.tsv_file))
            self._fp = open(self.tsv_file, 'r')
            self.pid = os.getpid()


class TSVWriter(object):
    def __init__(self, tsv_file):
        self.tsv_file = tsv_file
        self.lineidx_file = op.splitext(tsv_file)[0] + '.lineidx'
        self.tsv_file_tmp = self.tsv_file + '.tmp'
        self.lineidx_file_tmp = self.lineidx_file + '.tmp'

        self.tsv_fp = open(self.tsv_file_tmp, 'w')
        self.lineidx_fp = open(self.lineidx_file_tmp, 'w')

        self.idx = 0

    def write(self, values, sep='\t'):
        v = '{0}\n'.format(sep.join(map(str, values)))
        self.tsv_fp.write(v)
        self.lineidx_fp.write(str(self.idx) + '\n')
        self.idx = self.idx + len(v)

    def close(self):
        self.tsv_fp.close()
        self.lineidx_fp.close()
        os.rename(self.tsv_file_tmp, self.tsv_file)
        os.rename(self.lineidx_file_tmp, self.lineidx_file)
